In the field of workpiece transfer systems, a technique is disclosed in my copending U.S. application, Ser. No. 452,327, filed Dec. 22, 1982, in which a transfer beam is moved parallel to itself along an overall path comprised of a vertical or other predetermined lift path followed by a substantially horizontal curved path, followed by a vertical or other predetermined lowering path. A series of one or more mechanical hands mounted on this transfer beam are utilized to grasp and transfer workpieces from one set of positions to another, as exemplified by the progressive transfer of workpieces along a transfer line. The motion of the transfer beam is created, in part, by the movement of a carriage along a structural support beam, on which are mounted two rotating crank arms which support and drive the transfer beam through crankpins while rotating with respect to the carriage and transfer beam. In this arrangement, the mechanical hands are rigidly connected to the transfer beam, and therefore a given workpiece is lowered and deposited at the end of a transfer stroke in the same spatial orientation in which it had been picked up and lifted at the beginning of the transfer stroke.
Applications arise in which it is desirable or necessary to alter the spatial orientation of a given workpiece as it is being transferred from its pickup to its deposit point. It is one object of this invention to provide a system in which the spatial orientation of a mechanical hand and the workpiece it carries is altered during the transfer motion and that this be accomplished by employing the relative motion of the crank arms with respect to the transfer beam.
In most applications, it is desirable or necessary that the spatial orientation of a workpiece not be altered during the vertical lifting and lowering portions of the transfer stroke, since this would create interference problems with the pallets, fixtures, or other workholding devices from which a workpiece is removed or into which it is delivered. It is another object of this invention to provide a system in which the spatial reorientation of a given workpiece is generated only during the substantially horizontal portion of the transfer path, and that the spatial orientation remain substantially fixed during the lift and lower portions of the transfer path.
Other objects and features of the invention will be apparent in the following description and claims in which the best modes of the invention are set forth together with the principles of operation and details to enable persons skilled in the art to practice the invention.